I am having the same issue.
We are working on animations for a full 360° board. The board size is 21504x1152. If I render that size the output is squished. I figured out that if I render at a 2:1 ratio the output looks correct but its now a massive render dimension (21504x10752). The only way to save render time is to use the Render Region under render settings to render only the area I need, the 21504x1152 and the rest of the extra space is black.
I am attaching images of my Render settings and sample renders. My CV-VRcam settings are Equirectangular, Pole Merge top set to None, Pole merge bottom set to None.
It would be great if I could render without the extra black. Does rendering this extra black space increase render time at all?